Funny. ALT[176] for me does _. It's ALT[248] that does °.
That's all from the "old" IBM Extended Character Set. Here's the list:
255 [* see below]
254 _
253 ²
252 n
251 _
250 ·
249 •
248 °
247 _
246 ÷
245 _
244 _
243 _
242 _
241 ±
240 _
239 _
238 _
237 _
236 _
235 _
234 _
233 _
232 _
231 _
230 µ
229 _
228 _
227 ¶
226 _
225 ß
224 _
223 _
222 _
221 |
220 _
219 _
218 +
217 +
216 +
215 +
214 +
213 +
212 +
211 +
210 -
209 -
208 -
207 -
206 +
205 -
204 |
203 -
202 -
201 +
200 +
199 |
198 |
197 +
196 -
195 +
194 -
193 -
192 +
191 +
190 +
189 +
188 +
187 +
186 |
185 |
184 +
183 +
182 |
181 |
180 |
179 |
178 _
177 _
176 _
175 »
174 «
173 ¡
172 ¼
171 ½
170 ¬
169 _
168 ¿
167 º
166 ª
165 Ñ
164 ñ
163 ú
162 ó
161 í
160 á
159 ƒ
158 P
157 ¥
156 £
155 ¢
154 Ü
153 Ö
152 ÿ
151 ù
150 û
149 ò
148 ö
147 ô
146 Æ
145 æ
144 É
143 ÿ
142 Ä
141 ì
140 î
139 ï
138 è
137 ë
136 ê
135 ç
134 å
133 à
132 ä
131 â
130 é
129 ü
128 Ç
127
126 ~
125 }
124 |
123 {
122 z
121 y
120 x
119 w
118 v
117 u
116 t
115 s
114 r
113 q
112 p
111 o
110 n
109 m
108 l
107 k
106 j
105 i
104 h
103 g
102 f
101 e
100 d
099 c
098 b
097 a
096 `
095 _
094 ^
093 ]
092 \
091 [
090 Z
089 Y
088 X
087 W
086 V
085 U
084 T
083 S
082 R
081 Q
080 P
079 O
078 N
077 M
076 L
075 K
074 J
073 I
072 H
071 G
070 F
069 E
068 D
067 C
066 B
065 A
064 @
063 ?
062 >
061 =
060 <
059 ;
058 :
057 9
056 8
055 7
054 6
053 5
052 4
051 3
505 2
049 1
048 0
047 /
046 .
045 -
044 ,
043 +
042 *
041 )
040 (
039 ‘
038 &
037 %
036 $
035 #
034 "
033 !
032 space
031
030
029
028
027
026
025
024
023
022
021 §
020 ¶
019
018
017
016
015 ¤
014
013 [space]
012 [nasty!]
011
010 [line feed]
009 [tab]
008
007
006
005
004
003
002
001
000
* ALT[255] under MS-DOS produces a "space" that is not a space, but appears as one. It's a valid filename character and allows DOS to have filenames that appear as X MARINE vs. XMARINE. It was always handy under DOS for creating a filename that was more resistant to erasure or invocation unless the user knew about ALT[255]. A regular "space" is an invalid character in DOS.
Under DOS, the IBM ECS did things differently than it does under Windows. For instance, there was a group of characters that did "box" lines and double "box" lines for creating boxes around text and making crude drawings in the earlier word processors such as the venerable WordStar (still, in my opinion, the greatest word processor ever) and WordPerfect. It also had the bulk of the Greek alphabet, including omega.
Dean